Q57. Consider the following transformation involving first order elementary reaction in each step at constant temperature as shown below. $A + B$ Step $1 C \xrightarrow { \text { Step } 2 } P$ Some details of the above reactions are listed below. Step Rate constant ( $\mathbf { s e c } ^ { - \mathbf { 1 } }$ ) Activation energy ( $\mathbf { k J } \mathbf { ~ m o l } ^ { - \mathbf { 1 } }$ )
| 1 | $\mathrm { k } _ { 1 }$ | 300 |
| 2 | $\mathrm { k } _ { 2 }$ | 200 |
| 3 | $\mathrm { k } _ { 3 }$ | $\mathrm { Ea } _ { 3 }$ |
If the overall rate constant of the above transformation $( k )$ is given as $k = \frac { k _ { 1 } k _ { 2 } } { k _ { 3 } }$ and the overall activation energy $\left( \mathrm { E } _ { \mathrm { a } } \right)$ is $400 \mathrm {~kJ} \mathrm {~mol} ^ { - 1 }$, then the value of $\mathrm { Ea } _ { 3 }$ is $\mathrm { kJmol } ^ { - 1 }$ (nearest integer)